Controllable pitch propeller mechanism



Jan. 6, 1948. G. w. HARDY 2,433,990

CONTROLLA BUE PITCH PROPELLER MECHANISM Filed Aug. 13, 1943 5Sheets-Sheet l I55 [54 1/15 ,5 veancm. 3 67 1. 86 m .uum 9 /6/ I63INVENTOR.

GORDON W. HARDY 56 I By 7 l I 4:07 (W.

ATTORNEY Jan. 6, 1948; G, w, HARDY 2,433,990

QONTROLLABLE PITCH PROPELLER MECHANISM Filed Aug. 13, 1943 Sheets-Sheet3 ELM; ---/25 r 'A -'-20: I 4 ---/2e 7 V N 44 v J/ I I Z0 mvron GORDON.W- HARDY BY 20 6 l. I g 7 h4 AT TORNE Y Jan. 6, 1948. 3, w, HARDY2,433,990

CONTROLLABLE PITCH PROPELLER MECHANISM Filed Aug. 15, 1943' '5Sheets-Sheet 4 I I 62 I IIIHH' l I @l' MI C) 4 a! 970 La 70 I H9 (2 I vi 7 II me 44 57; w 3 4 l 20" i l 4 r 62 53" I] 65 6 34.

III A l /:a0 a 6/ INVENTOR. GORDON W. HARDY ATTORNEY Jan. 6, 1948."2,433,990

G. w. HARDY CONTROLLABLE PITCH PROPELLER MECHANISM Filed Aug. 13, 1943 5Sheets-Sheet 5 REVERIHBLE MOTO R v FEQTHEEING 8M0 REVERSE PoTcN flTOMRTIC STOP CONTROL INVENTOR. GORDON W. HARDv ATTORNEY Patented Jan. 6,1948 CON TROLLABLE PITCH PROPELLER MECHANISM Gordon W. Hardy, ClevelandHeights, Ohio, assignor to The Marquette Metal Products Company,Cleveland, Ohio, a corporation of Ohio Application August 13, 1943,Serial No. 498,492

3 Claims. (Cl. 170-163) 1 This invention relates to a controllable pitchpropeller mechanism and to a control system for adjusting the pitch ofthe blades while the craft served by the mechanism is in motion. Theobjects include provision of the following:

1. Arrangement for positive and accurate propeller blade control foreffecting any pitch variation that could be desired and wherein therotated weight is reduced substantially to a minimum and balanced.

2. An adjustable pitch propeller mechanism in which the blades areaccurately, hydrostatically locked in the desired positions at alltimes, and:

2a. Wherein the locking pressures resisting pitch changing movement inopposite directions may easily be adjusted to effect the steadiest andmost efiicient possible performance of the mechanism.

3. A new type of electro-hydraulic propeller pitch control.

4. A new type of governor regulated adjustable pitch propellermechanism.

5. A fluid pressure operated adjustable pitch propeller mechanism inwhich the pitch variation is accomplished by concurrently appliedpressure and suction.

6. An improved manner of supplyin from a stationary source, hydraulicfluid to a pitch adjusting servo-motor which rotates with the propellerand/or for supplying such fluid to the rotating assembly for otherpurposes as will be described.

7. An adjustable pitch propeller capable of multi-range blade adjustmentwherein the rotated parts are of light weight; the center of gravity isrelatively close to the outer main hearing support of the propellershaft, and the propeller can easily be fitted to any conventional typeof propeller driving shaft without changing the same in any way.

8. An efficient and balanced system for supplying de-icing fluid anddistributing the fluid to all parts of the propeller mechanism which arelikely to accumulate ice.

9. Means for de-icing the hub surfaces including those at or near thecenter of rotation where the rotational speed is least.

10. A simple and easily operated control apparatus for accomplishing alldesirable pitch adjustments and including various safety features.

Other objects of the invention will become apparent from the followingdescription of the embodiment shown in the drawings; wherein Fig. 1 isan axial central sectional assembly view of the propeller mechanismmounted on a supporting and driving shaft;

Figs. 2, 3, 4 and 5 are transverse sectional assembly views taken asindicated by lines 2-2 etc. to 5--5 on Fi 1;

. Fig. 6 (sheet 2) is a propeller blade shank and 2 mounting detailsection as indicated at 66 on Fig. 3;

Fig. 7 (sheet 3) is a sectional detail view taken as indicated at Fig. 4showing a normalpitch-limitinglatch mechanism;

Fig. 8 (sheet 4) is mainly a mechanical fluid circuit diagram showingthe manner in which the blades are operated hydraulically to changetheir pitch and released to perform more than ordinary pitch changes,and also showing how the hydraulic working pressures are initiallyadjusted and subsequently controlled and limited;

Fig. 9 is mainly an electrical diagram further showing the controlsystem, and

Fig. 10 is a fragmentary sectional detail view of a yieldable mountingor anchorage device for a fluid distribution unit of the propellerassembly, taken as indicated at l0l0 on Fig. 1.

GENERAL DISCUSSION; COPENDING CASES Some of the features of the presentadjustable pitch propeller mechanism hereof are shown in my copendingapplication Serial No. 476,398, filed February 19, 1943; and the presentcase, in respect to the manner of supplying de-icer fluid to thepropeller blade surfaces, is, in a sense, a continuation of myapplication Serial No. 491,037, filed Junelfi, 1943, which became PatentNo. 2,423,700. The adjustable pitch propeller mechanism I hereof differsgenerally from that of the first above mentioned application in that thepresent one operates to adjust the blades through the intermediary ofhydraulic fluid moved under the control of an operator (e g. pilot) orautomatically in response to engine speed change, whereas the bladesaccording to my said first mentioned application are mechanicallyadjusted by reactive forces imposed upon gearing in the propellermechanism under control of an operator or suitable automatic means suchas a centrifugal governor not disclosed in that applica- HUBCONSTRUCTION The hub 2 is made as a high tensile steel shell (e, g.forged steel) with a spheroidally formed hollow central wall portion 3from which tubular integral arms 4 extend radially, shown as threeinnumber, equally spaced about the axis of rotation, namely the fixed axisof a drive shaft 5 projecting from an engine or motor of the craftserved. The main support for the hub is constituted by a light weighthigh tensile steel hub car- BLADE MoUNrrNcs; EQUALIZING GEARING Theblades, shank portions 8 of which are shoWn' in Figs. 1, 3 and 6, aresupported for free turning movement about the radial axes of therespective arms 4 and within said arms on bearing assemblies includingrollers it} and thrust bearing elements ll retained inposition in muchthe same manner as are the similar bearing elements of my applicationSerial No. 476,398. The blades are strongly secured at buttress threadeffects l2 to half shell sections which complement each other to formmounting sleeves H3. The sleeves I3 lie partly within inner bearing racesleeves M for the rollers Iii and are fastened, as at screw threads l5and by central screw threaded studs llijto enlarged shank-or hubportions I! of blade-pitch-adjusting bevel gears i8 having rigid pilotsupports I9 at their inner ends on the hub carrier 6.

' The blade pitch-adjusting bevel gears :8 are inzero backlash' meshwith complementary teeth of a master or blade-pitch-equalizing andadjustinggear 20 as brought out by comparison of Figs. 1 and 3. The gear20 is supported for rotation about the axis of the drive shaft and isreadily turnable relative to said shaft for simultaneously'adjusting allthe blades to the same effective pitch angles. The support for andconstruction of the gear 20 are described later herein.

Referring further to theblades (Figs; "3 and 6) outward movement of eachblade mounting assembly described above is prevented by abutmentthrough'the bearing elements H with adjustably threadedrings 22 in theouter ends of the tubular arms 4, and the rings are held in adjustedposition taking up all end play by locking plate ass'emblies 2 3.

BLADE DE-ICING; OTHER FEATURES As shown by Figs. 3 and 6 the bevel gearhubs ll are hollow and laterally apertured at 2 3 so as to-receiveflexible portions 25 of supply tubes 25 for de-icer fluid (one for eachblade). The hollow buttpiece 21 of the particular blade constructionshown-provides a space in each blade for carrying the fluid from theflexible tube portions 25 to within the blades, as through connectingmetal tubes 28 entering the respective shanks of the blades throughopenings 29 (Fig. 6) in outer end wall portions 30 of the gear hubs H.The tubes 28' extend as at 28' within core body portions 3| 7constituting metalshells 32) and along the leading edge portions of theblades for as much of the length of said blades as required for fulldeicing, being apertured as at 33 for communication with the bladesurface as more fully eXplained in my said application Serial No.491,037.

BLADE ASSEMBLY FEATURES It should ben'oted that the inner ends of thetubes 28 are inserted through the openings 29 (Fig. 6) before the blademounting assemblies are completed to the extent of screwing in the gearhubs at'l5 and inserting and tightening the studs 15. Assembly ispossible notwithstanding the threaded connection at E5, and that theshell halves I3 are tightly pressed against the blade shank by thebearing sleeve it, because until the studlB is inserted the tube 28 willmerely" move in anorbit within the hollow shank piece 2? of the blade asthe hub ll is screwedinto place.

(e. g. plastic filler for blade-surface- The shell halves are madefrom'a single fully machined tube, spat afterwards lengthwise intohalves, and the threads at l5 are made the reverse of the threads of thestud 16 for opposite Y tightly intoplace.

clamping ring I3 is shown in Figs. 3 and 6 for locking effect when thestud is finally turned A slightly taper-threaded forcing the outer endportions of the split sleeve sections very tightly against the shank orbutt 'portion of the blade illustrated. Tightening of the clamping ringis a final assembly operation on the various blade units.

The connections between the flexible tubes 25 and the inner free ends ofthe tubes 28 are made through the open ends of the gears l8 before saidgears are in's'erted through the hub arms 4 and, afterward, the othernecessary connections -of'the tubes are "made through the still openou-ter end of the hub 2,- or, in other words, before the master gear 20is"iristalled. The manner in which fluid is supplied'to the tubes 26during rotation of'the hub will beexplained later.

HUB CONSTRUCTION (CONTINUED) Efiicz'ent distribution of massReferring'further to'the carrier 6 (Figs. 1 and 3)" said carrier isshown having a central tapered bore '35 which is'wedgedonto the shaft 5by a nut 38: engaging threads"?! of the shaftinthe plane "of the gears18' and lying within and "in spaced relation'to a tubular terminalportion '38 of the carrier which has radial cylindricalposts 39constituting'thesupports forthe pilotbearings I?) of the bevel gears l8.The nut '3'6'has a light weight forwardly projecting tubular portion 4i]which extends beyond theentire' hub assembly"except for a spinner or hubend cover 42 and 'associated'parts to be described later; andthe-outer'end of 'the extension Ml has capstanwrench holes at M to jamthe nut tight against a shoulder' lt of the carrier.

It is to-be understood that the drive shaft and carrier connection asherein shown and'just'described is'f'or example only; Other styles ofshafts (e. g; splined'shafts) on the heavier types of aircraft wouldrequire a different arrangementbut that" would not essential'ly or'materially change the present mechanism and construction.

The tubular portion 33 of 'the' hub carrier 6 forms apilot'beari'ngsupport fortheequalizing andbl'a'de adjusting' master gear 2fl;'but anelongated tubular hub a l of the gearhasa free turning fairly "s'ri igfit-"on the tubular "shank lll of the nut 36 as a main support'forsaidgear 28. The-hub carrier 6 has on the engine side of the hub 2' acircular flange" 45, lying 'Very 'close' to the bevel gears 18 toconserve arrial s'pacej and which is turned rearwardly 'afi' ifito'make'asnug fitting stepped joint with an intuinedend flange fill-ofthe hub' 2. The'flanges are'fastenedtogether as by appropriate screws45. The relatively thickwalled tubular portion '49 of the 'carrier 6projecting toward the engine-"and in which the principal portion ofthe'tapered bore 'ffi for the shaftf5 is formed, provides a support fora fluid distributor or manifold assembly and ducts for fluid suppliedtherethroughas'will bedescribed later herein.

BALANCED, DOUBLE AcrINcfPIrcH ADJUSTING SERVO-MOTOR At' the "outer endof the hub; 2 and-"fastened securely to the hub at a flange n -thereof;similar to the flange 41; is a servo-motor housing 50, preferably offorged aluminum or other light weight, strong metal to reduce as much asposible cantilever-supported weight at the outer hub end. The housing59, inwardly from its attaching flange 5|, slidingly abuts the mastergear 20 at 52 and maintains the latter in close meshing (zero backlash)relation to the gears l8. The abutment with the gear face 52 can benicely adjusted by means of thin shims between the flanges 4i and 5!,removed in servicing if necessitated by'occurrence of wear of the gearteeth.

The forward reduced end of the housing Si) is formed to provide asealing chamber for a flexible oil-sealing assembly 53 of conventionalform surrounding the outer end 20 of the hollow hub 40 of the gear2ilsealing thereagainst. Outwardly beyond the sealing chamber thehousing carries a locking key for the hub-assemblysecuring nut 35, inthe form of a cotter pin 55 as shown. The tubular end of the nut has, ofcourse,

a series of openings for the cotter pin, not shown.

The pitch-adjusting servo-motor, indicated generally at 6!) in Figs. 1,5 and 8 (latter two on sheet 4) and which is operated by a hydraulicactuator or master motor Bl, Figs. 5, 8 and 9 is fully balanceddynamically and in respect to force reactions and comprises twocylinderplunger assemblies constituted by substantially identicalcylinders 62 (sleeves as shown) and complementary pistons or plungers 63with cupshaped sealing discs 630. at their ends, all operativelysuported by the housing 56]. In the particular construction shown thepistons 63 are preferably light weight bronze (e. g. Toban bronze) andslide in steel sleeveswhich constitute the cylinders 62. The latter, asshown particularly in Fig. 5, are pressed into complementary parallelbores 54 in the housing 56 which bores are closed at their outer ends asby identical caps or plugs 65 threaded into the housing 50.

The sleeves 62 are laterally open intermediately of their ends andadjacent each other, being cut away as at 6% in partial approximateregistration with a central bore 61 of the housing 55) containing thehub 20 of the master (equalizing) gear 2E5 which has spur gear teeth 2%formed thereon for meshing (zero backlash) relationship with rack teeth63 on the respective pistons or plungers 63. The rack teeth are formedon parallel cut-away portions of the respective plungers intermediatelyof their ends so that the forces applied by the plungers to the gearteeth are approximately along the axes of the plungers for minimizinglateral thrust on the latter.

FLUID SUPPLY SYSTEM (IN PART) Hydraulic fiuidis fed to the servo-motorcylinders 62 from generally parallel bores 68 and $9 in the housing 56(see Figs. 1 and 8) which communicate with the cylinder ends throughlateral short bores 16 (Fig. 5). The bores 68 and 69 are served withfluid through obliquely extending passages H and "52 respectively(Fig. 1) which lie in a plane coincident with the hub axis, so thatfittings 13 (Fig. 1), used to connect the passages H and 12 withrespective feed tubes '15 and it, are balanced about the hub axis. Thetubes 15 and 16 pass through holes in the housing 50 and their rearwardends are connected, as exemplified by the fitting 11, Fig. 1, withrespective parallel axially extending bores 18 in the thickened tubularpart 49 of the hub carrier 6. Only the bore 18 which supplies the tube76 is illustrated. The

tube .15 is connected to another of said axially 6 extending bores 18formed in the part 49 circumferentially spaced from the illustratedbore.

Two other bores 18 beside the ones which serve the tubes 75 and F6 areformed in the carrier part 49 (purpose described later), and all thebores are closed at their rear ends, toward the engine, as by plugs 19,one being shown. Each of the bores 18 communicates, through a respectiveshort radial bore (one shown) exclusively with a different one of a setof parallel annular supply chambers or channels 8|, 82,,83 and 84surrounding and in sliding sealed relation to the smooth circularperiphery of the part 49 of the hub carrier.

SEMI-FLOATING FLUID MANIFOLD Fluid Supply System (Continued) The supplychannels 8l84 are contained in a rigid tubular manifold-constitutingportion 85 of a metal housing member 86 Whichportion 85 is substantiallycoextensive with the carrier portion 49 and has a yieldable anchoragewith the engine, shown in Fig. 10, so that the manifold, although fixedin position, does not require centering with respect to the carrier butcan float on the carrier. As shown in Fig. 10 a depending bracketportion 87 of the housing 86 has a bore 88 parallel to the driven shaft5 and in which a spool-like sleeve 89 of elastic compressible material(e. g. synthetic rubber) is snugly seated as by a force fit. The sleevein turn receives and is radially expanded by a stud 90 fastened to theengine housing, a small portion of which is indicated at 9i. The supportafforded by the device shown in Fig. 10 is sufiicient to relieve thepropeller hub carrier of having to support the principal weight of thehousing 86, yet said housing can nevertheless float slightly formaintaining concentricity with the carrier portion 49.

One supply tube 93 (for feed channel 80) is shown as secured to themanifold portion 85 of the housing 86 by a fitting 94. The interior ofthe fitting 94 communicates with theeiTective channel space 3i through ashort radial bore 95 in the manifold 85 and passages (not shown) formedbetween two adjacent sheet metal sealing ring retainer shells of channelshape respective to sealing rings 8| which are oppositely positioned soas to constitute the channel 8| in bearing yieldably against theadjacent peripheral surface of the tubular portion 49 of the carrier 6.The other manifold channels 82, 83 and 84 are formed similarly to theone just described.

FURT ER FEATURES'OF MANIFOLD SYSTEM The channels formed by the opposedpairs of sealing ring assemblies (yieldable rings and rigid shells orcasings) are prevented from communicating with each other by reason ofclose fitting abutment of the backs of the non-paired casings and closefitting (press fit) peripheral contact between each of the casings andthe bore of the portion 85 of the housing 86 in which the sealing ringsare held in close abutment (back to back and face to face) as between anannular end plate 85 at one end of the sealing ring assembly generallyand an inturned flange 86' at the other end. The pair of sealing ringscould be further isolated by interposed resilient compressible gaskets,though I have not found such expedient necessary.

DE-ICER FLUID DISTRIBUTION area-sec priate posit on around themanifeidfi The fitting for thejchan'ne1841is shown at91. "Thesupplytube" 98 for that particular fitting and themanifoldchannel'td andrespective conduits 26 served thereby (blade de-icing' conduits"previously" described) is connected as to a reservoir for (le -icingfluid (not shown) The reservoir or its "discharge pipe,would have asuitable pump actuatable atthe willof the pilot or other operator forsupplying the de-icer fluid at the proper times. The manifoldor'distributor channel 84 has three equally spaced axiallyextendingdischarge bores "I8. Each'of' the other channels has but one suchdischarge bore.

Two of thethree'outletfittings; corresponding to 11 Fig-l, andwhichareconnected respectively to the three paranei blade-de i'cing' outletbores 18, just-mentioned a re indicated in Fig. 3 at IBI. One is markedI02 and that constituting, in effect, a Y or T-' fitting-one'branchofwhich, at I03, has a flexible extension IE3 leading through a hole inthe servo-'motor-housirig 5!] to a hub-de-icing distributor nozzledevice Iilt (Fig. l only)"moun t'ed centrally of the spinner or cap 42.The other branch'of the Y or T- fitting I02 and both of the fittingsIill connect with; the blade de-ic'ing system tubes 26 (Figs; 3 and- 6)'already described.

HUB Jim-Iona The spinner-supported nozzle I09 hasseveral radiallydisposed outlet jet openings I05; two of which are shown. The jetoutlets lie in a low pressure area of the spinner created by deflectionof slipstream due to' the forward projection of thenozzlebody so thatde-icer 'fluid supplied to the jet opening will be distributedover thespinrierfroin several points where the fluid can then flow rearwardly'over'the spinner, hub and blade shank portions. v r v I The spinnershell'42 is secured as by wired-on screws I61 (wires not shown) to theouter flange portion of the servo-motor housing as a last operation-inassembling the propeller unit described above; and the' flexible de-icerfluid tube section I03 which connects with thespinnersupported nozzledevice Itil has to be made long enough to permit connection with saidnozzle device before thespinner is secured to the hub.

"Since ice always tends to form first on the central portion of -thehub-which rotatesatlowest peripheral speed the application of de-icerfluid to that region assists greatly inde-icing the blades. Aconsiderable portion of the ice formed on the blades -is;usuallystartedas; accumulations first formed on the hub and then caused to flowoutwaidlyfby centrifugal force to the blades,viz: lacier" elreet.

"CONTROLLED PITCH LIMIT STOP MECHANISM Referring further to the manifolddistributor channels'8I-'-84' it isjassumed that the channels 8Ifa nd82are connected 'to respectivepressure Chamber spaces of the masterhydraulic actuator GI as brought out s' c'h'eniatically inFigs."8 and 9(sheetsffl' and 5); that the third channel (83) supplies through "itsassociated axial bore 18 and fittiiigf such' as I? a tube IIO right'Fig.3, inside the hub. Thatfparticular tube (I I0) also leads throughtheservo motorhousing as do the tubes 15 and I6 forconnection with apitch range selector latch-abutment mechanism III illustrated in detailin Fig. '7 ('sh'eet"-3) and' also indicated, schematically on the fluidcircuit diagram Fi 8. Ji' ne iiu i j *o t leif i ch ni m I I 11 namelytd'pretent tnbiauesrremneing shifted below and" above" minimum" andmaximum pitch angles appropriate for forward driving of'the ship, whileenabling angular movement of the blades 'on their swivelmountings belowminimum normal pitch for reverse (1. e. for braking)"and above ,maximumnormal p'itch (he. for feathering). "As illustrated in Figsfll and '7the surface 52 of themaster' gear 20 is indented at regions H3 and II4;'and between those indentations 'is' a deeper indentation I'I5. Normallyseated in the depression I I5 is a latch block I I'I'in a non-circularguide bore I I8 of a latch mechanism housing II9. The'latch block hasfastem I20 projecting slidably through a partition'wall I2I of the housinginto a cylinder bore in'whicha piston part I22 of the stern' slides. Aspring I23ina vented'upper 'partlof the cylinder normally biases thelatch block II? toward whatever indented face (H3, H4, or H5) of thegear 20 thebl'ock may beadjacent.

To operate the latch'block to master-gear-releasing position, relativeto abutment surfaces II5a and H51) defining opposite circumferentially'spac'edlimits 0f the indentation H5, fluid is supplied under pressurethrough the distributor channel 83, tube H0 and a passagefl25 to thecylinder bore below vthe piston I22. The latch block cannot be liftedforwardly out'of the indentations H3 and H4 by over-supply of fluidthrough the tube III]. A

Once the latch block ii? is withdrawn from the indentation H5 and thegear 2E3 then moved to position one of the other indentations inoperative alignment with the b1ock,'the fluid force which withdrew theblock'may then be released with assurance that the gear will finally bearrested in full feathering or safe reversepitch' position, whichever isselected as the desired "abnormal pitch. However; as in Fig. 9,'whereinthe tube III is shown'connectjed to the cylinder I20 a handactuatableplunger I2! and afplunger retaining latch is providedas at I22automatically to'hold the fluid pressure injthe line Illi'sufiicient tocause the latch block II! to remain out of range of the stops HM and 5buntil release of the latch I22 by the operator. Such latch I22 onthejhand actuator for the pitch limit release latjch I I'I enables theoperator to adjust blade pitch at will as from a very' low pitch throughthe normal angles determined bythe' abutm'ents I Iiia, andI I51) andtherebeyond past the normally limitedhigh pitch.

Theangular relationships of the abutment surfaces I I5a, IISb'andIISaand II ia (Fig. 4 only) are or may be the same as thoseofthecorresponding fi-pitl'zh 'limit stops of *mykpphcation Serial No.476,398. The master hydrauli motor' 6| may be operated wholly manuallyin 'simple installations.

' Fruin'SYs'i-EM SCHEMA'TIC; MAsfcER' ACTUATOR Reference to thehydrauhcactuator fluid system as shownin Fig. 8 will assist in a betterunderstanding ofthe mechanismhereof. In Fig. 8 the piston'I'ZiEl'of themaster? hydraulic motor or actuator is shown in a position assumed to bethelimit of its stroketothe right, which, by forcing fluid through thetubes'le and "i6 and cross connecting tubes "68 andfieof'theservomotorcylinders; has moved theblades to' the fullfeathering position, bringing the "appropriate limitabutments (I IM orIIda) against the latch blockIII. Thefabutinents ofthe gear zfl are shcn th h, jd rf l fa a e W t hn or the plungers 63 of thesrild-rhotbr 60,which could, theoretically at least, be the mechanical arrangement,result being the same.

The master hydraulic motor BI may be arranged in strict accordance withmy application Serial No. 480,023, filed March 22, 1943 entitledHydraulic actuator. In common therewith, the plunger I30 hereof isdriven. by a reversible electric motor I32, a control system for whichis shown in Fig, 9 and explained later herein. The motor drives a screwI33 directly or through reduction gearing, preferably the latter (notshown) so that the motor can be small and of light weight and requirevery little current.

When current to the reversible motor I32 is cut off, friction andinertia of the screw I33 and the hydraulic load immediately arrests theplunger I30. The screw is inherently self-locking, insuring that theblades will remain indefinitely in adjusted position until furthermovement is imparted to the actuator piston I30.

Comeonnnn HYDRAULIC LOADING E'rc.

To charge the hydraulic system with fluid small hand-operable pumps areshown at I35 and I36 having inlets I3I continuously immersed in fluid ina storage reservoir I38 and with outlets connected, as throughone-way-operating or check valve chambers I39 and I40, with respectiveends of the master cylinder. The charging apparatus or its equivalentcan be placed anywhere in the ship; but preferably is Within easy reachof an operator so that the pressure in either side of the system can beincreased at any time. Thus the system can always be kept fully chargedregardless of slight leakage, should such occur; but, mainly, thearrangement enables controlled flutter or vibration resisting orcushioning of the blades as may be found desirable at diiferent speeds.Hydraulic fluid alone, without entrapped air and in vertically rigidconduits, is somewhat com ressible and therefore may be made to havevariable cushioning and vibration damping effects. If the compressioncan be adjusted the tendency for the blades to flutter can often bechecked altogether and in any event the vibration can be dampedconsiderably or eliminated by resistance of hydraulic columns; andwhatever vibration continues to occur can be prevented or partiallyprevented from being transmitted to the engine. Pressure gages connectedwith the opposite ends of the master cylinder can be used to inform theoperator of the instantaneous pressures resisting opposite pitch changemovement of the blades.

MOTOR-PROTECTIVE AUXILIARY PITCH LIMIT CONTROL Adjustable, electricallyoperated contacts I42 and I43 of a feathering and reverse pitchautomatic stop control device I4I may be used to protect the motor I32against continued current supply when stalled. The device, in a sense,aug,

ments the extreme pitch limit abutments 3a and H411 by causing currentto cease to be supplied to the motor I32 when the propeller blades reachfull feathering and maximum permitted reverse pitch positions. Thecontacts may be engaged for control operation by anelectricalground-constituting portion of the mechanism, for'instance asliding key I44 on'a sleeve portion of the master piston I30 which keyprevents said piston from turning in its cylinder.

ADJUSTABLE CONSTANT SPEED Con-r1201.

Fully automatic pitch control for constant speed 10 may be had throughthe intermediary of a speed responsive governor device driven by thepropeller or engine thereof. The governor I50, Figs. 2 and 9, controlsthe reversible electric motor consequent upon speed variations withinadjustable limits and at different speed settings.

A vertical governor drive shaft I5! (shown in horizontal position inFig. 2) is turned at relatively slow speed by the engine shaft throughthe intermediary of helical gearing including a driving gear I52 fixedon the hub carrier portion as within the housing 86 and a pinion I 53rigid on the shaft I5I. A fly-ball head I54 has ball arms I55 pressingwith increasing force against a slidable control head I55 proportionalto in crease in speed. Movement of the governor control head by the ballarms is resisted by a speeder spring I5! (partially omitted) thecompressive force of which spring may be adjustably altered by a speederplug I58 for change of speed setting, or, in other words, adjusting thevalue at which the governor will hold the engine speed by causingcompensating variations in pitch angles. The ultimate operation of thegovernor is conventional in adjustable pitch propellers; but

the manner in which the constant speed is maintained has uniquefeatures.

Moron CONTROL BY GOVERNOR Th control head I 55 moves a "ground contactI60 alternately against two opposed insulated electrical conductorterminals I 6| and I52 which are adjustable toward and away from eachother as by screws I63 and I64 respectively.

The speed is held more accurately, by more fre-' quent pitchadjustments, when the insulated contacts I6I and I62 are more closelyspaced. The conductors of the contacts I6I and IE2 cause, respectively,clockwise or counterclockwise rotation of the driving motor I32 of thehydraulic master or actuator for the blade adjusting mechanism.

Prrcn AND SPEED Srnncron The continuous speed (pitch) is selectedand setby adjustment of flexible torque shaft I65 (Figs. 2 and 9) connected tothe speeder plug at One end through a pinion and rack mechanism I60, I61of conventional form and at the other end with a selector knob I'I0.(Fig.9 only) having a pointer I10 which indicates the instantaneousspeed settings by reference to appropriate marks on an associated dialIII as the knob is turned either way from a normal speed CONTROL DIAGRAMReferring further to the control diagram, Fig.

9, 'four snap switchs are shown which require manual adjustment, saidswitches being markedf A, B, C and D. Th switch A is a thermal cut-- outswit'ch interposed between a feed wire I'I5,

leading from a power source (e. g. battery) I16 to the switch, and afeed wire I 11 leading to a central trunk terminal N8 of the motor I32.The battery is grounded as to the engine mounting,

and additional terminals I19 and I80 of the;

-motor are arranged to be grounded either diand .I 6 I. already,describedj' The contacts ,I 62 a and I6I arerarranged .to be,.placed.inseries with the switches C and. B, respectively, by manipulation ofsaidswitches. Ifthe motorcircuit is grounded.

throughithe wire I8l which .connects'flwith the switch crthermotoroperates in the required di:

rection to move the blades toward. low pitch and reverse. pitchposition, and if. the motor. is grounded through the wire I82,- which.connects with switch D, the motor turns in the reverse di-- rection,toward high pitch and feathering ,positions.

The control finger pieces or arms I 84 and I85 of the switchesC andD,respectively, are shown in. off position in full lines,'as are theswitch arms.

of all four switches A to D. Whenarms I84 and I85 areflicked to theright, th governor- In assumes automatic pitch control or regulation byvirtue ofconnecting-thetwo wires .I8I and I82 position the motor isenergized: manually; as for;

causing reverse pitch, through switch ground. wire or connection I88.Suchmanual control operation is done when the'switchD is'in the oilposition illustrated.. Similarly; .when: ,thisuswitch arm I85rot-switch" Dis smovedz'tovth'e left from. or: through i oft position(switch. C. then :ofi) the motor is: operatedtoward ifeathering; byestab lishing-;a-:circuit through aground wire-oncon nection I 89-:

The manual controllingoperations? justde-. scribed I: are" ordinarilyused only; when 1 reverse:

pitch or feathering operations-are desired; hence;

before accomplishments OfFthOSB'TEOPBIfifiOHS, thee limit-1 stop latch"releasing-is efiected'b'y move-' ment zof.'the=fplunger'- I 2 I to liftthe. stop pin or: block II! from engagement with the master:

equalizing gear, of the propellerat thecentral or intermediateindentation I I5 of said gear.

The switch B, asvshownrin'Fig; 9;'has=its movable contacti'armconnectedlto both" the adjust able'icontactss I421 and3 I43i'of" the:-feath'eringr and reverseapitch automatic control device already:

described ias @tlirough' fa all He I '9 B and a fixed co operating?contact ofTthe' switchr: B? is i normally connected .1 to thee. batterythrough" a: line I9I shownias 'branch'ing'ifrom zthe motor r'trunk feedwire ITI between Ethe -switch A andxzthenmotor'.The=motorriprotectivercircuit :or' control arrangement; .in:the'rparticularr form :sh-own; requires .the'

switch Bin'jOI'CIGI" that when one :of the contacts I 42: and I431temporarilyshort circuits the: systerm in shunt with the motor,a-s-athroughlines- I98 I91 and the-thermal .cut out switch A, causingthe-latter; promptly-to break: the motor feed i circuit, the contact I4Ior I43 which has engaged the ground terminal I44 canb'e'moved away fromsaid? terminal. Otherwise (considering; for:'the

moment, ,I Siliconnected s=p.ermanentlyi'-tofq I 9'] 1 the operatorcould notrestartthemotor to reverse; itrfromi rthGr directionofsr-otati'on which brought the econtacts-i. I42, I44; or I43,:. I 44.;together; and;

caused.-the'-,temp orary short circuits It-sshou ldabe :noted-thatin-ithe .eventithe.:governor-controlled operation: previously?-described causes, operation otithemoton. I32 until on of;

the limiting abutments II I5a and I IE1; .is: engaged by, theQlimit,stopelementJ I'I dangerous overheating of themotorwouldbe prevented byautomatic .operation .of..the.thermal .switch A :tofloff-f speedat.eiiicient R. P; ,M. of the engines position before damage to themotor can occur.

The circuit arrangement .describedabove is. designed to use standardsnap switches and, in the case of switch A, a standard thermal cut-ofl,

snapswitch is used By providing switches built, especially to serve theessential purposes described, the numberof manipulatable elements, couldbe c-onsiderablyreduced and the. control operations thereby.possiblysimplified.

CONTROL SYSTEM OPERATION (EXAMPLES) Before flight is commenced, thepilot makesv certain that switches A'and.B..areon. and. C and Dare inautomatic positions; that the limit stop is released (block II? incondition. to. enter gear indentation I I5), and thattheflpitchselector-knob IIll is set at 'ornear normal speed setting. 7

For take-off or .climbing,'the pitch selector is moved to low-pitchsetting so. that the engine can accelerate properly.

In flight upon assuming? the adesiredrs'level or altitude the pitchselector knob isadjustedto normal or other desired position ,causingadjustment, through the governor, of the desired Thegovernor mechanismthen causes attainment .of automatic constant speed.

For normal landing, switches A andB. are still left in on? position; Cand D in automatic, and the pitch selectorv knob is moved tolow pitch(highR. P, M);

To. land .with brakingefiect, vthe first operation is to depress theplunger,- I2I for pitch limit stop release. The switch D is moved to"off position and switch 0 is then moved through ofi position toreversepitch position. Reversing of pitch is then accomplished automatiecally and will be limited by the engaged abut-.- ment NM or IIdacorresponding torreverse, and if the pilot leaves the switch C.- inreverse pitch position the motor circuit willjbenimmediately. broken byoperation of theautomatiostop con.- trol device I iI as described,through-operation. of the thermal cut-out switchA- To resume normaloperation after reverse, the limit stop release plunger latch.I22 is.released; switch B ismoved to oi'ff position; Cand D to automatic.positions, and A is thenclosed. The blades could, of course, be movedtoward normal setting by manual operation of themechanism throughtemporarily setting the switch D at feathering. The switch B is returnedto on position as soon as the motor I32 starts to turn.

For feathering, switches A and B are in on position, switch C *is moved'to off and 'Dto feathering positiom T'o'unfeather the blades fromiullfeathereol'position in which the automatic stop control' MI shortcircuits the system to stop the motor I32, the procedure issubstantially, the same as described .in the next preceding paragraph.after. full .reverseipitch operation has obtained.

I claim:

1. In combination with a variable pitch propeller having ablade-supporting hub, a hydraulic: servo-motor on the hub having opposednon-com municating displacement chambers, a master hydraulic cylinderand a piston therein, the oppos site ends of the cylinderbeinghydraulically per-.-- manently connected with respectivedisplacement chambers of the servo-motor, positively acting; meansconnected to the piston. to move it back and forth in its cylinder andtolock it in adjusted positions thereby, to lock the blades, and: pump- 13ing means in respective sides of the hydraulic system to maintain,individually adjusted pressure in said sides.

2. In an adjustable pitch propeller, a hub having blades sWivelledthereon, mechanism revoluble with the hub for adjusting the blades todetermine their pitch, said mechanism including per manentlyinterconnected gear elements constituting equalizing gearing connectingthe blades, a pair of pitch limiting stops on one of said elements ofthe gearing, a plunger on the hub normally positioned between saidstops, hydraulically operated 'means arranged to move the plunger out ofsaid position to enable abnormal pitch changing movement in at least onedirection, said means including a latch for automatically holding theplunger out of the path of movement of the stops, and hydraulicactuating GORDON W. HARDY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,156,103 Austin Apr. 25, 19391,878,358 Yates Sept. 20, 1932 2,237,191 Mills Apr. 1, 1941 2,229,058Dicks Jan. 21, 1941 1,887,053 Yates Nov. 8, 1932 1,886,891 Martens etal. Nov. 8, 1932 2,161,917 Forsyth et al. June 13, 1939 1,829,930Hele-Shaw et al. Nov. 3, 1931 2,296,348 Hoover Sept. 22, 1942 2,020,366McCallum Nov. 12, 1936 2,276,347 Ruths et al. Mar. 17, 1942 2,320,195Rindfleisch May 25, 1943 1,851,874 Seppeler Mar. 29, 1932 FOREIGNPATENTS Number Country Date 464,203 Great Britain Apr, 12, 1937 217,669Switzerland Apr. 16, 1942 18,445 Holland 1897 379,731 Italy Apr. 4, 1940449,407 Great Britain June 26, 1936 796,083 France Mar. 28, 1936 OTHERREFERENCES The Bee-Hive, May-June 1938, published by United AircraftCorp, East Hartford, Conn. (Copy in Div. 9.)

